Switch-operating means for bin alarms



Aug. 29, 1950 c. GRAY 2,520,500

SWITCH OPERATING MEANS FOR BIN ALARMS Filed July 30, 1947 es/e/g/y Gray L- I Z I;

#tfly m may MIW Patented Aug. 29, 1950 SWITCH-OPERATIN G MEANS FOR BIN ALARMS Chcsleigh Gray, Indianapolis, Ind, assignor to Blaw-Knox Company, Pittsburgh, Pa., a corporation of New Jersey Application July 30, 1947, Serial No. 764,796

4 Claims.

This invention relates to mechanism for operating a switch to indicate when a bin is nearly full or nearly empty.

Flexible diaphragms of canvas or rubber have been employed hertofore for actuating switches to indicate when the contents of a bin reach the desired upper level when being filled and a predetermined lower level when being emptied. These diaphragms are satisfactory for fine materials such as sand and cement but are not durable enough to withstand the abrasive action of coarser materials such as gravel, crushed rock or the like, used as aggregate in making concrete.

I have invented a novel switch-operating mechanism for this purpose composed entirely of metal and thus adapted to resist wear by abrasion from the material being handled. In a preferred form, I mount a tube open at the ends in the bin adjacent a Wall thereof. A plate is deflectably mounted in the tube, adapted to be tilted by the impact of material falling through the tube when the bin has been filled to an extent such that the material overflows the top of the tube. Tilting movement of the plate actuates a switch controlling signal means of any desired type. When the material in the bin has been depleted to an extent such that the material trapped in the tube is free to flow out of the lower end thereof, the plate returns to nor b mal position, resetting the switch and chang ing the indication. The tube is desirably com posed of telescoping sections permitting adjustment of its overall length. The apparatus may thus be set to operate at various heights of the material in the bin according to the particular conditions of any given installation.

The defiectable plate is preferably a disc-like paddle mounted on a shaft journaled in the tube on an axis transverse thereto. The shaft extends outwardly through the bin wall and has a lever thereon for operating the switch. A counterwei'ght on the lever tends to urge the plate toward horizontal position. A baffle plate in the tube slopes downwardly and inwardly over the shaft.

A complete understanding of the invention may be obtained from the following detailed description which refers to the accompanying drawings illustrating a present preferred embodiment. In the drawings,

Figure l is a partial vertical section through a wall of a bin showing the invention in elevation;

' Figure 2 is an elevation such as would be seen by looking on Figure 1 from the right, the wall of the bin being omitted; and

Figure 3 is a horizontal section taken along the plane of line TIL-III of Figure 2.

Referring in detail to the drawings, a bin i!) or other like container for granular material H includes a frame composed of spaced structural members I 2 and plates l3. While the invention may be applied to any type of bin or material container, the bin illustrated is open at the top and has a hopper bottom with a spout controlled by a suitable gate. Such construction is well known and is therefore not illustrated.

The apparatus of my invention indicated generally at (4- comprises a tube |5 open at the ends and disposed substantially vertically in the bin adjacent a wall thereof. In the illustrated embodiment, the tube comprises a pair of telescoping sections [5a and Lib. These sections are secured to the bin wall by straps i6, after being adjusted axially so as to bring the top of the section a to the level of the material in the bin at which filling should be discontinued and the bottom of the lower section to the level at which refilling of the bin should be started.

Bins for handling bulk material such as the aggregate used in making concrete are commonly filled by conveyors or elevators of the chain-bucket or other type. In order to reduce the frequency of filling operations, the bin should be filled as full as possible without running the risk of overflow. It is necessary to stop the operation of the filling equipment in time to prevent overflow and it is usually preferably to empty the conveying equipment of any material it has starter to deliver. The operator is usually not in a position to view the material in the bin directly and indicating means are accordingly provided to signal when the conveying equipment should be stopped as well as when it should be restarted after the material has been largeiy withdrawn from the bin. In order to insure con tinuous operation, the conveying equipment should be started while a certain minimum amount of material remains in the bin. These conditions determine the heights at which the top of the upper section and the bottom of the lower section of the tube l5, respectively, are positioned when mounted on the bin wall.

A transverse shaft I1 is journaled in alined bearings l8 intersecting the tube section IE?) on one side of the axis and welded thereto. A paddle in the form of a disc I9 is secured to the shaft ll. The paddle is shown as circular but may be of other suitable shape so long as its dimension parallel to the shaft I1 is small enough to permit deflection under the weight of a column of material accumulating in the tube IS. A baffle plate 20 slopes downwardly and inwardly above the shaft H. The lower inner edge of the plate is disposed at about the level of the shaft and slightly inwardly thereof so as to serve as a stop limiting counterclockwise rotation of the paddle IS.

The shaft 11, as clearly shown in Figure 3, projects outwardly through the wall of the bin. A lever 2| is secured to the projecting end of the shaft and is provided with an adjustable counterweight 22. The counterweight normally exerts a torque on the shaft ll tending to hold the paddle against the bailie plate 20. A switch 23 of the mercury-pool type is secured to the lever 21 in such position that its contacts are bridged when the lever and paddle are in the normal position in which they are shown in the drawings but are disconnected when the lever and. paddle are in their alternate positions indicated in chain lines. Any other suitable form. of switch. means actuated by tilting movement of thepaddle may be employed instead of the specifictype ofxswitch mentioned.

For the purpose of explaining. thev operationof the invention, it will first be assumed that the tube i5 is empty and that the bin in is in. the course of being filled. The material delivered into the bin, of course, piles up under the point of delivery and flows downwardly. from the apex of the pile, the level of the pile rising as the deliver of material continues. Because of the character of the material. (gravel, crushed rock or the like) there is no tendency for it to rise in the tube 55- as the bin. fills up: above the bottom thereof. When. the bin has been filled toa point such that material flowing down laterally from the apex of the pile enters the tube 15, the material falling therethrough strikes the paddle l9 and the weight of the material ac.- cumulating thereon soon suffices to tilt the-paddle and its supporting shaft through about. 90 The paddle is mounted ashort distance. above the bottom of the lower'tube section- I Ebtoinsure that it will be free to turn under the weight: of material accumulating thereon, without interference' from the material filling the bin. below the tube. This operates the switohE-dand causes operation of signal means of any desired type to inform the operator that the binis about. full. As above explained, the upper tube: sectionl-5a is preferably set so as to. permit the conveyor system to continue operation longenough; to clear itself of any material which has actually been started toward the bin, without causing overflow. The tube IE will ordinarily be filled to the top by the time the last of the material in the conveyor has been deliveredto the bin.

After the conveyor system delivering material to the bin has been shut down, batches of mate.- rial may be withdrawn from the bin by operating the control gate. No change in the switch-op.- erating mechanism of my invention occurs; until the material in the bin has been depletedto the extent such that the materialtrapped in the tube 15- is free to flow out of-the'lowerend thereof. Asthe material-is drawn from the bin-the cone existing at the top of thebin: on completion ofv the filling operation becomes-a conical depres sionbecause of the friction between thedescending material and the walls of the-bin. Thet-ma'- terial trapped in the tube; l5, therefore, does not begin to flow .outthe-lower endruntil the base angle of the inverted conical depression in the pile exceeds the angle of repose of the particular material being handled. Shortly after this condition has been reached, all the material in the tube 15 flows out through the bottom thereof whereupon the counterweighted lever 2| restores the paddle [9 to horizontal position, i. e., in engagement with the lower edge of the-baiiie plate 20. The resulting operation of the switch 23 changes the signal indication so that the operator will be informed that it is time to start the conveyor for refilling the bin. As indicated above, the bottom of the lower tube section l5b should be positioned so that this indication will be given while suflicient material remains in the bin to permit a few further batches to be measured from the bin while the conveyor gets underway and' starts the refilling operation.

It will be apparent that the invention is characterized by several important advantages. the first place, the apparatusv is rugged and sturdy and is Well adapted to withstand the wear to which it is necessarily subjected by reason of contact with the material being handled whichis usually highly abrasive. At the same time, the construction is simple so as to be positive in operation without requiring any particular attention or extensive maintenance. The telescoping tube sections permit a standard design of apparatus-to be applied to bins having a substantial range of heights. The single switch-operating mechanism, furthermore, serves to control the signalling means for both the full and empty condition of the bin. The bailie plate prevents accumulation of material above the bearings for the shaft on which the paddle is mounted.

Although I have illustrated and described but a preferred embodiment of the invention, it will be understood that changes in the details of construction may be made without departing from the spirit of the invention or the scope of the appended claims.

I- claim:

1. Signal-operating mechanism for indicating when a bin has been filled to a desired maximum with granular material and when withdrawals of said material have depleted it to a predetermined minimum, said apparatus comprising a tube open at the ends and disposed substantially vertically adjacent a wall of the bin, said tube being p0- sitioned with its top and bottom respectively approximating the levels at which said bin is full and at which said bin requires refilling, a plate pivotally mounted in the lower portion of said tube on an axis transverse thereto adapted to be displaced by the weight of a column of material thereabove, means permitting said plate to be so displaced as the filling of said bin approaches completion, and mean urgingsaid platetoward a substantially horizontal position;

2; A bin alarm for a bin. adapted to be periodicallyfilled with and emptied. of granular material, comprising. in combination,.a substantially open tube positioned within saidv bin in a. substantially vertical position, the top of said tube approximating the level to which said bin isto be periodically filled, the bottom of said tube approximating the level to which said bin is to be periodically emptied, a deflectable paddlepivoted adjacent said bottom and athwart said tube in normal position and adapted to be deflected; by granular material moving downwardly through said tube, means permittingsaid paddle to be so deflected as the filling of said bin approaches completion, indicating means operatedrbymovement of said paddle, and means to maintain said paddle in normal position unless so deflected, whereby the deflection of said paddle indicates said bin is substantially full and the restoration of said paddle to normal position indicates said bin is in need of refilling.

3. A bin alarm for a bin adapted to be periodically filled with and emptied of granular material, comprising in combination, a substantially open straight tube positioned within said bin in a substantially vertical position, the top of said tube approximating the level at which said bin is full and the bottom of said tube approximating the level at which the refilling Of said bin is desirable, said tube further having telescoping sections and adapted to make said top and bottom levels respectively adjustable, a deflectable plate positioned transverse to said tube in normal position and adjacent said bottom, said plate being pivotally connected to said tube and adapted to be deflected by granular material moving down- Wardly through said tube, said plate further being so pivoted a distance upwardly from said bottom of said tube at least equal to the length of said plate for clearance, indicating means operated by movement of said plate, and means to maintain said plate in normal position unless so deflected, whereby said plate is deflected when said granular material overflows the top of said tube indicating said bin is substantially full and said plate is returned to normal position when the level in said bin moves below the bottom of said tube permitting the granular material deflecting said plate to fall out of said tube.

4. A switch operating bin alarm for a bin adapted to be periodically filled with and emptied of coarse granular material, comprising in combination, a straight open vertical tube positioned within said bin adjacent one side thereof, the top of said tube being located approximately at the level at which said bin is in filled condition and the bottom of said tube being located at approximately the level at which the refilling of said bin is desirable, a horizontal paddle in said tube adapted to be engaged and deflected by granular material overflowing the top of said tube, a horizontal rotatable shaft extending through said tube to one side of the axis thereof, said shaft further being keyed to said paddle to permit the downward deflection thereof and being positioned above the bottom of said tube substantially the height of said paddle when so deflected, a counterweighed lever connected to one side of said shaft outside said tube to return said paddle to horizontal position, a stop within said tube to prevent upward movement of said paddle above said horizontal position, and a switch in fixed engagement relative said lever, whereby when said bin becomes substantially full, granular material overflows into said tube and deflects and holds said paddle in deflected position to indicate said initiating filled condition, and to signal a refillable condition when said deflected paddle is released by said overflowing granular material falling out of the bottom of said tube when the level in said bin reaches said desirabl refilling level.

CHESLEIGH GRAY.

REFERENCES GITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 649,702 Moulton May 15, 1900 1,239,315 Stine Sept. 4, 1917 1,298,950 Hull Apr. 1, 1919 1,549,967 Grindle Aug. 18, 1925 2,286,144 Lien June 9, 1942 

